Construction machine energy regeneration apparatus

ABSTRACT

A construction machine energy regeneration apparatus includes: a movable weight provided in a construction machine and movable vertically; and a power-transmitting hydraulic circuit, which moves the movable weight upward by utilizing energy that is generated when a boom, an arm, or a bucket moves in a gravitational direction or energy that is generated when a brake is applied to bring a turning unit or a running unit to a stop, and utilizes potential energy of the movable weight as energy for driving the boom or the arm.

TECHNICAL FIELD

The present invention relates to a construction machine energy regeneration apparatus included in a construction machine that includes an operating part including a boom, a turning unit, or a running unit driven by a drive unit.

BACKGROUND ART

As one example of a conventional hydraulic excavator, there is a hydraulic excavator that causes an electric motor to regenerate electric power when, for example, reducing the speed of a turning unit, stores the regenerative electric power in a capacitor, uses the regenerative electric power stored in the capacitor to operate the electric motor via a controller and an inverter when turning the turning unit, and assists the rotation of a hydraulic motor with the torque of the electric motor (see Patent Literature 1, for example).

By thus using the regenerative electric power stored in the capacitor to assist the rotation of the hydraulic motor, the fuel consumption can be reduced.

CITATION LIST Patent Literature

PTL 1: Japanese Laid-Open Patent Application Publication No. 2005-290882

SUMMARY OF INVENTION Technical Problem

However, the above-described conventional hydraulic excavator needs to include the capacitor and the inverter as equipment for storing the regenerative electric power and utilizing the stored regenerative electric power when turning the turning unit. This causes an increase in cost, a high possibility of the occurrence of a failure, and in addition, size and weight increase. Moreover, the above-described conventional hydraulic excavator goes through multiple steps including: converting mechanical energy of the turning unit into electrical energy; temporarily storing the electrical energy; and then converting the electrical energy into mechanical energy again. Therefore, the overall energy regenerative ratio is not very high, which is another problem. Furthermore, the above-described conventional hydraulic excavator is unable to regenerate potential energy when the hydraulic excavator is in a motion different from turning (i.e., boom lowering, arm crowding, or bucket crowding).

The present invention has been made to solve the above-described problems. An object of the present invention is to provide a construction machine energy regeneration apparatus and a construction machine including the same, which make it possible to eliminate the capacitor and the inverter, thereby reducing the cost to be inexpensive, reducing failures, and reducing the size to suppress an increase in weight.

Solution to Problem

A construction machine energy regeneration apparatus according to the present invention is an energy regeneration apparatus of a construction machine, the construction machine including a first operating part and a second operating part, which are driven by a hydraulic fluid, the first operating part including a boom, a turning unit, or a running unit, the second operating part including an arm, a bucket, or an engine-assisting hydraulic motor. The construction machine energy regeneration apparatus includes: a movable weight provided in the construction machine and movable vertically; and a power-transmitting hydraulic circuit, which moves the movable weight upward by utilizing energy that is generated when the boom, the arm, or the bucket moves in a gravitational direction or energy that is generated when a brake is applied to bring the turning unit or the running unit to a stop, and utilizes potential energy of the movable weight as energy for driving the first operating part or the second operating part.

According to the construction machine energy regeneration apparatus of the present invention, the movable weight can be moved (e.g., swung) upward by utilizing energy that is generated when the boom or the like moves in the gravitational direction or energy that is generated when a brake is applied to bring the turning unit or the like to a stop. This makes it possible to store the potential energy of the boom or the like or the kinetic energy of the turning unit or the like as the potential energy of the movable weight.

Then, the boom, the turning unit, or the like can be driven by utilizing the potential energy of the movable weight.

Since the potential energy of the boom or the like or the kinetic energy of the turning unit or the like can be stored as the potential energy of the movable weight and utilized as described above, the fuel consumption of the construction machine can be reduced compared to conventional art.

The construction machine energy regeneration apparatus according to the present invention may include: a communication passage, through which a circuit of the first operating part or a circuit of the second operating part communicates with a circuit of the movable weight; and a switching valve, which is provided on the communication passage and which switches a flow direction of the hydraulic fluid in the communication passage. The switching valve may be configured to shift to a first position when the boom, the arm, or the bucket moves in the gravitational direction or when a brake is applied to bring the turning unit or the running unit to a stop, such that the hydraulic fluid flows through the communication passage and the switching valve to move the movable weight upward, and the switching valve may be configured to shift to a second position when the movable weight moves in the gravitational direction, such that the hydraulic fluid flows through the communication passage and the switching valve to drive the first operating part or the second operating part.

According to the above power-transmitting hydraulic circuit, the switching valve, which switches the flow direction of the hydraulic fluid in the communication passage, is provided on the communication passage, through which the circuit of the first operating part or the circuit of the second operating part communicates with the circuit of the movable weight. Therefore, potential energy or kinetic energy of the first operating part or the second operating part can be regenerated, and the regenerative energy can be utilized for driving the first operating part or the second operating part.

The construction machine energy regeneration apparatus according to the present invention may be configured such that the movable weight and a part of the power-transmitting hydraulic circuit have a function as a counter weight of the construction machine, and such that a total mass of the movable weight and the part of the power-transmitting hydraulic circuit is substantially equal to a mass of a counter weight required by the construction machine.

By adopting the above configuration, even though the hydraulic excavator includes the energy regeneration apparatus, the total mass of the hydraulic excavator can be made not to exceed the total mass of the hydraulic excavator that does not include the energy regeneration apparatus. This makes it possible to prevent an increase in power for operating the turning unit or the running unit, which is an operating part, as well as an increase in fuel consumption. Consequently, energy can be regenerated and utilized more effectively.

In the construction machine energy regeneration apparatus according to the present invention, the movable weight may be supported on a predetermined fulcrum and vertically swingable about the fulcrum by operation of a hydraulic cylinder.

By adopting the above configuration, the following technical advantages are provided. For example, in order to obtain great potential energy of the movable weight, it is necessary to move the movable weight vertically by a great moving distance. For this reason, it is necessary that the stroke of the hydraulic cylinder be great. However, considering the structure of the hydraulic cylinder, it is desirable that the stroke thereof be relatively small so that stable operation of the hydraulic cylinder will be realized. Accordingly, by providing the movable weight such that the movable weight is vertically swingable about the fulcrum, and setting a distance between the fulcrum and a connection where the hydraulic cylinder is connected to the movable weight to be suitably short, the moving distance of the center of gravity of the movable weight in the vertical direction can be made relatively great, and in addition, the stroke of the hydraulic cylinder for vertically swinging the movable weight by a predetermined angle can be set to be relatively small.

In the construction machine energy regeneration apparatus according to the present invention, the movable weight may be configured to be movable in a linear direction.

This makes it possible to provide an inexpensive construction machine energy regeneration apparatus with a simple structure and reduced failures.

In the construction machine energy regeneration apparatus according to the present invention, the movable weight may be supported on a predetermined fulcrum and vertically swingable about the fulcrum by operation of a hydraulic cylinder. The hydraulic cylinder may include a lifting cylinder and an assisting cylinder. A distance between the fulcrum and a connection where the lifting cylinder is connected to the movable weight may be set to be greater than a distance between the fulcrum and a connection where the assisting cylinder is connected to the movable weight. The power-transmitting hydraulic circuit may be configured to operate the lifting cylinder when the boom moves in the gravitational direction or when a brake is applied to bring the turning unit or the running unit to a stop, such that the movable weight swings upward, and the power-transmitting hydraulic circuit may be configured to operate the assisting cylinder when the movable weight swings downward to drive the first operating part or the second operating part.

By adopting the above configuration, the following technical advantages are provided. As described above, the distance between the fulcrum and the connection where the lifting cylinder is connected to the movable weight is set to be greater than the distance between the fulcrum and the connection where the assisting cylinder is connected to the movable weight. Accordingly, the pressure discharged from the assisting cylinder to lower the movable weight can be made higher than the pressure supplied to the lifting cylinder to raise the movable weight. Therefore, the pressure of the hydraulic fluid for driving the first operating part or the second operating part can be made high, which makes it possible to widen a pressure range within which the potential energy of the movable weight is utilized.

The construction machine energy regeneration apparatus according to the present invention may include: a solenoid pilot valve, which supplies a pilot pressure liquid to a pilot port of the switching valve; a control valve, which controls a pressure and a flow rate of the hydraulic fluid supplied to the first operating part or the second operating part; a remote control valve, which supplies a pilot pressure liquid to a pilot port of the control valve; pressure sensors, which measure a supply pressure and a discharge pressure of the hydraulic fluid of the first operating part or the second operating part, or measure output pressures of the remote control valve, and generate pressure signals; and a controller, which receives the pressure signals and transmits a command signal to the solenoid pilot valve based on the pressure signals.

As described above, based on an operation amount of the remote control valve for operating the boom, the turning unit, or the like and the supply pressure and the discharge pressure of the hydraulic fluid of the boom, the turning unit, or the like, the controller performs control of opening the switching valve via the solenoid pilot valve. This makes it possible to efficiently regenerate the potential energy or kinetic energy of the boom, the turning unit, or the like as the potential energy of the movable weight.

Advantageous Effects of Invention

The construction machine energy regeneration apparatus according to the present invention is configured to regenerate the potential energy of an operating part or kinetic energy based on inertial force, and utilize the regenerative energy for driving an operating part. This makes it possible to reduce the fuel consumption of the construction machine compared to conventional art.

Moreover, the construction machine energy regeneration apparatus according to the present invention makes it possible to eliminate, for example, a capacitor and an inverter for regenerating the potential energy of an operating part or kinetic energy based on inertial force, thereby reducing the cost to be inexpensive, reducing failures, and reducing the size to suppress an increase in the weight of the construction machine

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a hydraulic excavator including a construction machine energy regeneration apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram showing, in an exaggerated manner, a movable weight of the construction machine energy regeneration apparatus of FIG. 1.

FIG. 3 shows a hydraulic circuit of the hydraulic excavator of FIG. 1.

FIG. 4 shows a control circuit of a weight switching valve of FIG. 3.

FIG. 5 shows the state of the hydraulic circuit of the hydraulic excavator of FIG. 3 at the time of boom raising.

FIG. 6 shows the state of the hydraulic circuit of the hydraulic excavator of FIG. 3 when energy is regenerated at the time of boom lowering.

FIG. 7 shows the state of the hydraulic circuit of the hydraulic excavator of FIG. 3 when regenerative energy is utilized for arm pushing.

FIG. 8 shows a hydraulic circuit of a hydraulic excavator according to Embodiment 2 in a state where regenerative energy is utilized for bucket pushing.

FIG. 9 shows a hydraulic circuit of a hydraulic excavator according to Embodiment 3 in a state where regenerative energy is utilized for operating an engine-assisting hydraulic motor and arm pushing.

FIG. 10 shows a hydraulic circuit of a hydraulic excavator according to Embodiment 4 in a state where energy is regenerated when a brake is applied to bring a turning unit to a stop.

FIG. 11 shows the state of the hydraulic circuit of the hydraulic excavator of FIG. 10 when regenerative energy is utilized for arm pushing.

FIG. 12 is a schematic diagram showing, in an exaggerated manner, a movable weight of a construction machine energy regeneration apparatus according to Embodiment 5.

FIG. 13 is a schematic diagram showing, in an exaggerated manner, a movable weight of a construction machine energy regeneration apparatus according to Embodiment 6.

DESCRIPTION OF EMBODIMENTS

Hereinafter, Embodiment 1 of a construction machine energy regeneration apparatus according to the present invention is described with reference to FIG. 1 to FIG. 11. A construction machine energy regeneration apparatus 11 is included in a construction machine such as a hydraulic excavator 15, whose operating part includes, for example, a boom 12, a turning unit 13, and a running unit 14 shown in FIG. 1 and FIG. 2 and is driven by a hydraulic fluid discharged from a hydraulic pump 28 (drive unit) shown in FIG. 3. The construction machine energy regeneration apparatus 11 includes a movable weight 16 movable vertically and a power-transmitting hydraulic circuit 17A (see FIG. 3).

In the description herein, the boom 12, the turning unit 13, or the running unit 14 is referred to as a first operating part, and an arm 19, a bucket 20, or an engine-assisting hydraulic motor 52 (see FIG. 9) is referred to as a second operating part.

The power-transmitting hydraulic circuit 17A shown in FIG. 3 is configured to move the movable weight 16 upward by utilizing, for example, energy that is generated when the boom 12, the arm 19, or the bucket 20 moves in the gravitational direction or energy that is generated when a brake is applied to bring the turning unit 13 or the running unit 14 to a stop, and utilize the potential energy of the movable weight 16 as energy for driving the first operating part such as the boom 12 or the second operating part such as the arm 19.

In the hydraulic excavator 15 shown in FIG. 1, the turning unit 13 is turnably mounted on the running unit 14 via a turning mechanism 18. The boom 12 is mounted to the front central part of the turning unit 13, such that the boom 12 is swingable up and down. The arm 19 is mounted to the distal end of the boom 12, such that the arm 19 is rotatable in a vertical plane. The bucket 20 is mounted to the distal end of the arm 19, such that the bucket 20 is rotatable in a vertical plane.

FIG. 2 is a schematic diagram showing, in an exaggerated manner, the movable weight 16, which is provided at the rear of the turning unit 13 of the hydraulic excavator 15. The movable weight 16 has a function of storing the gravitational force of the boom 12 or the like as potential energy, and has a function as a counter weight of the hydraulic excavator 15.

Specifically, the movable weight 16 and a part of the power-transmitting hydraulic circuit 17A have a function as a counter weight of the hydraulic excavator 15, and the total mass of the movable weight 16 and the part of the power-transmitting hydraulic circuit 17A is set to be substantially equal to the mass of a counter weight required by the hydraulic excavator 15.

The shape and the material of the movable weight 16 shown in FIG. 2 are equivalent to those of a conventional counter weight. The movable weight 16 is provided at the rear of the turning unit 13, and is positioned at the opposite side to the boom 12 with respect to the turning mechanism 18. The movable weight 16 is provided such that the movable weight 16 is movable vertically in a linear direction along guides 25. A weight hydraulic cylinder 21 is provided under the movable weight 16.

The weight hydraulic cylinder 21 supports the movable weight 16 such that the movable weight 16 is movable vertically in the linear direction. The weight hydraulic cylinder 21 is provided between the lower part of the movable weight 16 and a frame 13 a of the turning unit 13. The weight hydraulic cylinder 21 includes: a cylinder portion 21 a whose proximal end is fixed to the frame 13 a of the turning unit 13; and a piston rod 21 b whose distal end is swingably connected to the lower part of the movable weight 16 via a connection 26.

FIG. 3 shows a hydraulic circuit 27 including the power-transmitting hydraulic circuit 17A of the hydraulic excavator 15. The hydraulic circuit 27 includes communication passages 22 (22 a, 22 b, and 22 c) and a weight switching valve 24. It should be noted that, in FIG. 3, circuits other than those of the boom 12 and the arm 19 are omitted.

The communication passages 22 are passages through which the circuits of the first operating part and the second operating part, including boom communication passages 53 (53 a and 53 b) and arm communication passages 54 (54 a and 54 b), communicate with movable weight communication passages 55 (55 a and 55 b).

The weight switching valve 24 is connected to the communication passages 22, and serves to switch the flow direction of the hydraulic fluid in the communication passages 22.

The weight switching valve 24 shifts to a first position (II) when the boom 12, the arm 19, or the bucket 20 moves in the gravitational direction or when a brake is applied to bring the turning unit 13 or the running unit 14 to a stop, such that the hydraulic fluid flows through the communication passages 22 and the weight switching valve 24, and thereby the movable weight 16 can be moved upward.

The weight switching valve 24 shifts to a second position (III) when the movable weight 16 moves in the gravitational direction, such that the hydraulic fluid flows through the communication passages 22 and the weight switching valve 24, and thereby the first operating part including the boom 12 or the second operating part including the arm 19 can be driven.

Specifically, for example, ports A and B of the weight switching valve 24 shown in FIG. 3 are connected to a head-side port of the weight hydraulic cylinder 21 and a rod-side port of the weight hydraulic cylinder 21 via the movable weight communication passages 55 a and 55 b. Ports B and C of the weight switching valve 24 are connected to each other. A port T of the weight switching valve 24 is connected to a tank 32, and a port P of the weight switching valve 24 is connected to a discharge port of the hydraulic pump 28 via the communication passage 22. A port D of the weight switching valve 24 is connected to the arm communication passage 54 a via the communication passage 22 a. The communication passage 22 a is provided with a check valve.

The hydraulic circuit 27 shown in FIG. 3 includes control valves for the first operating part including the boom 12 and control valves for the second operating part including the arm 19. Each of these control valves serves to control the pressure and the flow rate of the hydraulic fluid that is supplied to the first operating part or the second operating part.

FIG. 3 shows an arm control valve 56 and a boom control valve 57.

The arm control valve 56 serves to control the pressure and the flow rate of the hydraulic fluid that is supplied to an arm hydraulic cylinder 37. Ports A and B of the arm control valve 56 are connected to two ports (rod-side and head-side ports) of the arm hydraulic cylinder 37 via the arm communication passages 54 a and 54 b. A port T of the arm control valve 56 is connected to the tank 32 via a tank communication passage 60, and a port P of the arm control valve 56 is connected to the discharge port of the hydraulic pump 28 via a pump communication passage 61.

The boom control valve 57 serves to control the pressure and the flow rate of the hydraulic fluid that is supplied to a boom hydraulic cylinder 39. Ports A and B of the boom control valve 57 are connected to two ports (rod-side and head-side ports) of the boom hydraulic cylinder 39 via the boom communication passages 53 a and 53 b. A port T of the boom control valve 57 is connected to the tank 32 via a tank communication passage 62, and a port P of the boom control valve 57 is connected to the discharge port of the hydraulic pump 28 via a pump communication passage 63.

FIG. 3 shows remote control valves, each of which serves to supply a pilot pressure liquid to pilot ports of a corresponding one of the above control valves.

FIG. 3 shows an arm remote control valve 64 and a boom remote control valve 65.

The arm remote control valve 64 is operated by an operator and serves to supply the pilot pressure liquid to pilot ports X and Y of the arm control valve 56 through communication passages 64 b and 64 a.

The boom remote control valve 65 is operated by the operator and serves to supply the pilot pressure liquid to pilot ports X and Y of the boom control valve 57 through communication passage 65 b and 65 a.

First to tenth pressure sensors PS1 to PS10 serve to: measure a supply pressure and a discharge pressure of the hydraulic fluid of the first operating part or the second operating part; measure output pressures of the remote control valves; and generate pressure signals as electrical signals. FIG. 3 shows first to sixth pressure sensors PS1 to PS6.

The first and second pressure sensors PS1 and PS2 serve to measure output pressures of the boom remote control valve 65, which occur in the communication passages 65 a and 65 b, and generate pressure signals as electrical signals.

The third and fourth pressure sensors PS3 and PS4 serve to measure output pressures of the arm remote control valve 64, which occur in the communication passages 64 a and 64 b, and generate pressure signals as electrical signals.

The fifth and sixth pressure sensors PS5 and PS6 serve to measure output pressures that occur in the boom communication passages 53 b and 53 a, which are connected to the boom hydraulic cylinder 39, and generate pressure signals as electrical signals.

The hydraulic circuit 27 shown in FIG. 3 further includes a control circuit 70 shown in FIG. 4. The control circuit 70 shown in FIG. 4 includes first and second solenoid pilot valves 71 and 72 and a controller 73.

The first solenoid pilot valve 71 shown in FIG. 4 serves to supply a pilot pressure liquid to a pilot port Pia of the weight switching valve 24 shown in FIG. 3 in accordance with a current flowing through a first signal line 71 a. The pressure source of the pilot pressure liquid is a hydraulic pressure discharged from a control hydraulic pump 74.

The second solenoid pilot valve 72 serves to supply a pilot pressure liquid to a pilot port Pib of the weight switching valve 24 shown in FIG. 3 in accordance with a current flowing through a second signal line 72 a. The pressure source of the pilot pressure liquid is a hydraulic pressure discharged from the control hydraulic pump 74.

The controller 73 serves to electrically receive electrical pressure signals outputted from the first to tenth pressure sensors PS1 to PS10, and transmit electrical command signals to the first and second solenoid pilot valves 71 and 72 based on the electrical pressure signals.

Next, functions of the construction machine energy regeneration apparatus 11 are described with reference to FIG. 5 to FIG. 11. FIG. 5 shows the state of the hydraulic circuit 27 and the control circuit 70 of FIG. 3 and FIG. 4 of the hydraulic excavator 15 at the time of raising of the boom 12. When the operator operates the boom remote control valve 65 for raising of the boom 12, the spool of the boom control valve 57 shifts to the position (III), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the boom hydraulic cylinder 39 as indicated by a bold solid line, and thereby the boom 12 can be raised to a desired height.

At the time, the pressurized oil discharged from the hydraulic pump 28 is supplied also to the weight switching valve 24. However, since the port P is closed at the time, the pressurized oil is not supplied to the weight hydraulic cylinder 21. Accordingly, the movable weight 16 remains stopped without being raised or lowered.

FIG. 6 shows the state of the hydraulic circuit 27 and the control circuit 70 of FIG. 3 and FIG. 4 when energy is regenerated at the time of lowering of the boom 12. When the operator operates the boom remote control valve 65 for lowering of the boom 12, the spool of the boom control valve 57 shifts to the position (II), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the boom hydraulic cylinder 39 as indicated by a bold solid line, and thereby the boom 12 can be lowered to a desired height. At the time, pressurized oil discharged from the boom hydraulic cylinder 39 is supplied to the weight switching valve 24.

Then, the controller 73 electrically receives electrical pressure signals outputted from the fifth and sixth pressure sensors PS5 and PS6, and transmits an electrical command signal to the second solenoid pilot valve 72 based on the electrical pressure signals. In response, the spool of the weight switching valve 24 shifts to the position (II), such that pressurized oil discharged from the boom hydraulic cylinder 39 is, as indicated by a bold one-dot chain line, supplied to the weight hydraulic cylinder 21 through the weight switching valve 24, and thereby the movable weight 16 can be raised.

At the time, based on an operation amount of the boom remote control valve 65 for operating the boom 12, and the supply pressure and the discharge pressure of the hydraulic fluid of the boom 12 (i.e., electrical pressure signals from the fifth and sixth pressure sensors PS5 and PS6), the controller 73 performs control of opening the weight switching valve 24 via the second solenoid pilot valve 72. This makes it possible to efficiently regenerate the potential energy of the boom 12 as the potential energy of the movable weight 16.

FIG. 6 illustrates an example in which the potential energy of the boom 12 is regenerated as the potential energy of the movable weight 16. However, alternatively, the potential energy of the arm 19, the bucket 20, or the like can be regenerated as the potential energy of the movable weight 16 although it is not shown in the drawings.

FIG. 7 shows the state of the hydraulic circuit 27 and the control circuit 70 of FIG. 3 and FIG. 4 when regenerative energy is utilized for pushing of the arm 19. When the operator operates the arm remote control valve 64 for pushing of the arm 19, the spool of the arm control valve 56 shifts to the position (II), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the arm hydraulic cylinder 37 as indicated by a bold solid line and a bold one-dot chain line, and thereby the arm 19 can be swung in the pushing direction.

At the time, the controller 73 electrically receives electrical pressure signals outputted from pressure sensors (not shown) connected to the arm hydraulic cylinder 37, and transmits an electrical command signal to the first solenoid pilot valve 71 based on the electrical pressure signals. In response, the spool of the weight switching valve 24 shifts to the position (III), such that pressurized oil discharged from the weight hydraulic cylinder 21 is supplied to the arm hydraulic cylinder 37 through the weight switching valve 24 as indicated by a bold one-dot chain line, and thereby the arm 19 can be swung in the pushing direction. In this manner, regenerative energy can be utilized for pushing of the arm 19.

That is, as shown in FIG. 6, the movable weight 16 can be moved upward by utilizing energy that is generated when the boom 12 moves in the gravitational direction (i.e., when the boom 12 is lowered). In this manner, the potential energy of the boom 12 can be stored as the potential energy of the movable weight 16.

Then, as shown in FIG. 7, the potential energy of the movable weight 16 can be utilized to drive the arm 19 in the pushing direction.

Thus, the potential energy of the boom 12 can be stored as the potential energy of the movable weight 16 and utilized as described above. This makes it possible to reduce the fuel consumption of the construction machine compared to conventional art.

Further, as shown in FIG. 2, the movable weight 16 has a function as a counter weight of such a construction machine as the hydraulic excavator 15. The total mass of the movable weight 16 and a part of the power-transmitting hydraulic circuit 17A (17B and 17C in Embodiments 3 and 4 described below) is set to be substantially equal to the mass of a counter weight required by the construction machine.

Accordingly, even though the hydraulic excavator 15 includes the energy regeneration apparatus 11, the total mass of the hydraulic excavator 15 can be made not to exceed the total mass of the hydraulic excavator 15 that does not include the energy regeneration apparatus 11. This makes it possible to prevent an increase in power for operating the turning unit 13 or the running unit 14, which is an operating part, as well as an increase in fuel consumption. Consequently, energy can be regenerated and utilized more effectively.

Further, as shown in FIG. 2, the movable weight 16 is provided such that the movable weight 16 is movable in a linear direction. This makes it possible to provide an inexpensive construction machine energy regeneration apparatus 11 with a simple structure and reduced failures.

FIG. 8 shows a hydraulic circuit of Embodiment 2 of the present invention in a state where regenerative energy is utilized for driving the bucket 20.

A bucket control valve 58 serves to control the pressure and the flow rate of a hydraulic fluid supplied to a bucket hydraulic cylinder 38. Similar to the above-described configuration, the bucket control valve 58 is connected to the bucket hydraulic cylinder 38, the tank 32, and the hydraulic pump 28.

A bucket remote control valve 66 is connected to pilot ports X and Y of the bucket control valve 58 via communication passages 66 b and 66 a.

The seventh and eighth pressure sensors PS7 and PS8 shown in FIG. 8 serve to measure output pressures of the bucket remote control valve 66, which occur in the communication passages 66 a and 66 b, and generate pressure signals as electrical signals.

FIG. 8 shows the state of the hydraulic circuit 27 and the control circuit 70 of FIG. 3 and FIG. 4 when regenerative energy is utilized for pushing of the bucket 20. The state shown in FIG. 8 is different from the state shown in FIG. 7 in the following point: in the state shown in FIG. 7, regenerative energy is utilized for pushing of the arm 19, whereas in the state shown in FIG. 8, regenerative energy is utilized for pushing of the bucket 20.

Referring to FIG. 8, when the operator operates the bucket remote control valve 66 for pushing of the bucket 20, the spool of the bucket control valve 58 shifts to the position (II), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the bucket hydraulic cylinder 38 as indicated by a bold solid line and a bold one-dot chain line, and thereby the bucket 20 can be swung in the pushing direction.

At the time, the controller 73 operates in the same manner as in the case shown in FIG. 7, such that pressurized oil discharged from the weight hydraulic cylinder 21 is supplied to the bucket hydraulic cylinder 38 through the weight switching valve 24 as indicated by a bold one-dot chain line, and thereby the bucket 20 can be swung in the pushing direction.

In this manner, regenerative energy (i.e., potential energy of the movable weight 16) can be utilized for pushing of the bucket 20. This makes it possible to reduce the fuel consumption of the construction machine compared to conventional art.

FIG. 9 shows a hydraulic circuit 75 of Embodiment 3. In Embodiment 3, the hydraulic circuit 75 includes the power-transmitting hydraulic circuit 17B of the hydraulic excavator 15, and is configured such that the communication passage 22 a for the engine-assisting hydraulic motor 52 is added to the hydraulic circuit 27 shown in FIG. 3. FIG. 9 shows a state where the engine-assisting hydraulic motor 52 is driven by regenerative energy, and regenerative energy is utilized for pushing of the arm 19.

When the operator operates the arm remote control valve 64 for pushing of the arm 19, the spool of the arm control valve 56 shifts to the position (II), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the arm hydraulic cylinder 37 as indicated by a bold solid line, and thereby the arm 19 can be swung in the pushing direction.

At the time, the controller 73 electrically receives electrical pressure signals outputted from pressure sensors (not shown) connected to the arm hydraulic cylinder 37, and transmits an electrical command signal to the first solenoid pilot valve 71 based on the electrical pressure signals. In response, the spool of the weight switching valve 24 shifts to the position (III), such that pressurized oil discharged from the weight hydraulic cylinder 21 is supplied to the engine-assisting hydraulic motor 52 through the weight switching valve 24 and the communication passage 22 a as indicated by a bold one-dot chain line. As a result, the engine-assisting hydraulic motor 52 rotates, and thereby driving of the hydraulic pump 28, which is connected to the rotary shaft of the engine-assisting hydraulic motor 52, can be assisted.

In this manner, regenerative energy (potential energy of the movable weight 16) can be utilized for pushing of the arm 19. This makes it possible to reduce the fuel consumption of the construction machine compared to conventional art.

It should be noted that, as shown in FIG. 9, the port D of the weight switching valve 24 is connected to the oil inlet of the engine-assisting hydraulic motor 52 via the communication passage 22 a.

FIG. 10 shows a hydraulic circuit 76 of Embodiment 4. In Embodiment 4, the hydraulic circuit 76 includes the power-transmitting hydraulic circuit 17C of the hydraulic excavator 15, and is configured such that turning unit communication passages 69 a and 69 b are added to the hydraulic circuit 27 shown in FIG. 3 instead of the boom communication passages 53 a and 53 b, and also, check valves 78 a and 78 b, which guide oil flowing out of the turning unit communication passages 69 a and 69 b in one direction, are added. FIG. 10 shows a turning unit control valve 59.

The turning unit control valve 59 serves to control the pressure and the flow rate of a hydraulic fluid supplied to a turning unit hydraulic motor 36. Similar to the configuration previously described, the turning unit control valve 59 is connected to the turning unit hydraulic motor 36, the tank 32, and the hydraulic pump 28.

A turning unit remote control valve 67 is connected to pilot ports X and Y of the turning unit control valve 59 via communication passages 67 b and 67 a.

The ninth and tenth pressure sensors PS9 and PS10 shown in FIG. 10 serve to measure output pressures of the turning unit remote control valve 67, which occur in the communication passages 67 a and 67 b, and generate pressure signals as electrical signals. FIG. 10 shows a state where energy is regenerated when a brake is applied to bring the turning unit 13 to a stop.

For example, the operator operates the turning unit remote control valve 67 in order to apply a brake to bring the turning unit 13 to a stop while the turning unit 13 is turning in a reverse direction. In response, the spool of the turning unit control valve 59 shifts from the position (II) to position (I), such that the outlet side of the turning unit hydraulic motor 36 is blocked by the turning unit control valve 59.

In parallel with the above operation, the controller 73 electrically receives electrical pressure signals outputted from the ninth and tenth pressure sensors PS9 and PS10, and transmits an electrical command signal to the second solenoid pilot valve 72 based on the electrical pressure signals. In response, the spool of the weight switching valve 24 shifts to the position II, such that pressurized oil discharged from the turning unit hydraulic motor 36 is supplied to the weight hydraulic cylinder 21 through the weight switching valve 24 as indicated by a bold one-dot chain line, and thereby the movable weight 16 can be raised. It should be noted that, at the time, the turning unit hydraulic motor 36 sucks the pressurized oil from the tank 32.

In this manner, energy generated at the time of applying a brake to bring the turning unit 13 to a stop can be stored as the potential energy of the movable weight 16.

Then, at the time, based on the operation amount of the turning unit remote control valve 67 for operating the turning unit 13, and the supply pressure and the discharge pressure of the hydraulic fluid of the turning unit 13 (i.e., signals from the ninth and tenth pressure sensors PS9 and PS10), the controller 73 performs control of opening the weight switching valve 24 via the second solenoid pilot valve 72. This makes it possible to efficiently regenerate the kinetic energy of the turning unit 13 as the potential energy of the movable weight 16.

FIG. 10 illustrates an example in which the kinetic energy of the turning unit 13 is regenerated as the potential energy of the movable weight 16. However, alternatively, the kinetic energy of the running unit 14 can be regenerated as the potential energy of the movable weight 16 although it is not shown in the drawings.

It should be noted that, as shown in FIG. 10, the port P of the weight switching valve 24 is connected to the oil inlet port and the oil outlet port of the turning unit hydraulic motor 36 via a communication passage 36 a. The reference sign 77 in FIG. 10 indicates relief valves for controlling the discharge pressure of the hydraulic pump 28.

FIG. 11 shows the state of the hydraulic circuit 76 of the hydraulic excavator 15 of FIG. 10 when regenerative energy is utilized for pushing of the arm 19.

When the operator operates the arm remote control valve 64 for pushing of the arm 19, the spool of the arm control valve 56 shifts to the position (II), such that pressurized oil discharged from the hydraulic pump 28 is supplied to the arm hydraulic cylinder 37 as indicated by a bold solid line and a bold one-dot chain line, and thereby the arm 19 can be swung in the pushing direction.

At the time, the controller 73 electrically receives electrical pressure signals outputted from pressure sensors (not shown) connected to the arm hydraulic cylinder 37, and transmits an electrical command signal to the first solenoid pilot valve 71 based on the electrical pressure signals. In response, the spool of the weight switching valve 24 shifts to the position (III), such that pressurized oil discharged from the weight hydraulic cylinder 21 is supplied to the arm hydraulic cylinder 37 through the weight switching valve 24 and the communication passages 22 a and 54 a as indicated by a bold one-dot chain line, and thereby the arm 19 can be swung in the pushing direction. In this manner, the driving of the hydraulic pump 28 can be assisted.

As described above, regenerative energy (potential energy of the movable weight 16) can be utilized for pushing of the arm 19.

That is, as shown in FIG. 10, by utilizing the kinetic energy that is generated when a brake is applied to bring the turning unit 13 to a stop, the movable weight 16 can be moved upward. In this manner, the kinetic energy of the turning unit 13 can be stored as the potential energy of the movable weight 16.

Then, the arm 19 can be driven by utilizing the potential energy of the movable weight 16.

Thus, the kinetic energy of the turning unit 13 can be stored as the potential energy of the movable weight 16 and utilized as described above. This makes it possible to reduce the fuel consumption of a construction machine compared to conventional art.

Next, Embodiment 5 of the construction machine energy regeneration apparatus according to the present invention is described with reference to FIG. 12. A construction machine energy regeneration apparatus 43 according to Embodiment 2 shown in FIG. 12 is different from the construction machine energy regeneration apparatus 11 according to Embodiment 1 shown in FIG. 2 in the following point: in Embodiment 1 shown in FIG. 2, the movable weight 16 is provided such that the movable weight 16 is movable vertically in the linear direction along the guides 25, whereas in Embodiment 5 shown in FIG. 12, the movable weight 16 is supported on a predetermined fulcrum 44, such that the movable weight 16 is vertically swingable about the fulcrum 44.

The fulcrum 44 supporting the movable weight 16 as shown in FIG. 12 is provided on the frame 13 a of the turning unit 13. The weight hydraulic cylinder 21 is provided under the movable weight 16.

The weight hydraulic cylinder 21 is provided such that the movable weight 16 is vertically swingable about the fulcrum 44 when the cylinder 21 expands and contracts.

The weight hydraulic cylinder 21 is provided between the lower part of the movable weight 16 and the frame 13 a of the turning unit 13. The proximal end of the cylinder portion 21 a is swingably connected to the frame 13 a of the turning unit 13 via a connection 45. The distal end of the piston rod 21 b is swingably connected to the lower part of the movable weight 16 via the connection 26.

The construction machine energy regeneration apparatus 43 according to Embodiment 5 shown in FIG. 12 provides technical advantages as follows. For example, in order to obtain great potential energy of the movable weight 16, it is necessary to move the movable weight 16 vertically by a great moving distance. For this reason, it is necessary that the stroke of the weight hydraulic cylinder 21 be great. However, considering the structure of the weight hydraulic cylinder 21, it is desirable that the stroke thereof be relatively small so that stable operation of the weight hydraulic cylinder 21 will be realized, and the hydraulic pressure for raising and lowering of the movable weight 16 can be set to be relatively high.

Accordingly, by providing the movable weight 16 such that the movable weight 16 is vertically swingable about the fulcrum 44, and setting a distance L1 between the fulcrum 44 and the connection 26 where the weight hydraulic cylinder 21 is connected to the movable weight 16 to be suitably short, the moving distance of the center of gravity of the movable weight 16 in the vertical direction can be made relatively great, and also, the stroke of the weight hydraulic cylinder 21 for vertically swinging the movable weight 16 by a predetermined angle can be set to be relatively small, and in addition, the hydraulic pressure for raising and lowering of the movable weight 16 can be set to be relatively high.

Other than the above-described features, Embodiment 5 is the same as Embodiment 1 shown in FIG. 2. Common components between Embodiment 1 and Embodiment 5 are denoted by the same reference signs, and the description of such components is omitted.

Next, Embodiment 6 of the construction machine energy regeneration apparatus according to the present invention is described with reference to FIG. 13. A construction machine energy regeneration apparatus 48 according to Embodiment 6 shown in FIG. 13 is different from the construction machine energy regeneration apparatus 43 according to Embodiment 5 shown in FIG. 12 in the following point: in Embodiment 5 shown in FIG. 12, one weight hydraulic cylinder 21 is provided between the movable weight 16 and the frame 13 a of the turning unit 13, whereas in Embodiment 6 shown in FIG. 13, for example, one lifting hydraulic cylinder (weight hydraulic cylinder) 21 and one assisting hydraulic cylinder 49, i.e., a total of two cylinders, are provided between the movable weight 16 and the frame 13 a of the turning unit 13.

Similar to Embodiment 5 shown in FIG. 12, the movable weight 16 shown in FIG. 13 is supported on a predetermined fulcrum 44. The movable weight 16 is provided such that the movable weight 16 is vertically swingable about the fulcrum 44. The lifting hydraulic cylinder 21 and the assisting hydraulic cylinder 49 are connected to the movable weight 16 via two connections 26 and 50, respectively.

The lifting and assisting hydraulic cylinders 21 and 49 include piston rods 21 b and 49 b, respectively. The distal ends of the piston rods 21 b and 49 b are provided with the connections 26 and 50, respectively. The connections 26 and 50 are swingably connected to the movable weight 16. A distance L2 between the fulcrum 44 and the connection 26 and a distance L3 between the fulcrum 44 and the connection 50 are set such that the distance L2 of the lifting hydraulic cylinder 21 is greater than the distance L3 of the assisting hydraulic cylinder 49. It should be noted that the reference sign G shown in FIG. 13 indicates the position of the center of gravity of the movable weight 16.

Although not shown in the drawings, the power-transmitting hydraulic circuit is configured to guide pressurized oil to the weight hydraulic cylinder 21 to expand the weight hydraulic cylinder 21 at the time of swinging the movable weight 16 upward, and discharge pressurized oil from the assisting hydraulic cylinder 49 to contract the assisting hydraulic cylinder 49 at the time of swinging the movable weight 16 downward.

The lifting and assisting hydraulic cylinders 21 and 49 include cylinder portions 21 a and 49 a, respectively. The proximal ends of the cylinder portions 21 a and 49 a are swingably connected to the frame 13 a of the turning unit 13 via connections 45 and 51, respectively.

As described above, by setting the distance L2 between the fulcrum 44 and the connection 26 of the lifting hydraulic cylinder 21 connected to the movable weight 16 and the distance L3 between the fulcrum 44 and the connection 50 of the assisting hydraulic cylinder 49 connected to the movable weight 16, such that the distance L2 of the weight hydraulic cylinder 21 is greater than the distance L3 of the assisting hydraulic cylinder 49, the pressure of pressurized oil discharged from the assisting cylinder 49 to lower the movable weight 16 can be made higher than the pressure of pressurized oil supplied to the lifting hydraulic cylinder 21 to raise the movable weight 16. Accordingly, the pressure of the hydraulic fluid for driving the first operating part or the second operating part can be made high, which makes it possible to effectively utilize the potential energy of the movable weight.

Other than the above-described features, Embodiment 6 is the same as Embodiment 1 shown in FIG. 2. Therefore, the description of the other features of Embodiment 6 is omitted.

Although the present invention is applied to a hydraulic excavator in the above-described embodiments, the present invention is also applicable to other construction machines, for example, a crane.

Although hydraulic oil is taken as an example of the hydraulic fluid in the above-described embodiments, a liquid different from hydraulic oil may be used as the hydraulic fluid.

Although FIG. 7, FIG. 8, FIG. 9, and FIG. 11 show examples in which the regenerated energy is utilized for driving the arm 19 or the bucket 20, the regenerated energy can also be utilized for driving the boom 12, for example.

INDUSTRIAL APPLICABILITY

As described above, the construction machine energy regeneration apparatus and the construction machine including the same, according to the present invention, make it possible to eliminate the capacitor and the inverter, thereby providing excellent advantages of reducing the cost to be inexpensive, reducing failures, and reducing the size to suppress an increase in weight. Thus, the present invention is suitably applicable to a construction machine energy regeneration apparatus and a construction machine including the same.

REFERENCE SIGNS LIST

11 construction machine energy regeneration apparatus

12 boom

13 turning unit

13 a frame

14 running unit

15 hydraulic excavator (construction machine)

16 movable weight

17A, 17B, 17C power-transmitting hydraulic circuit

18 turning mechanism

19 arm

20 bucket

21 weight hydraulic cylinder (lifting hydraulic cylinder)

21 a cylinder portion

21 b piston portion

22, 22 a, 22 b, 22 c communication passage

24 weight switching valve

25 guide

26 connection

27 hydraulic circuit

28 hydraulic pump

32 tank

36 turning unit hydraulic motor

36 a communication passage

37 arm hydraulic cylinder

38 bucket hydraulic cylinder

39 boom hydraulic cylinder

43 construction machine energy regeneration apparatus

44 fulcrum

45 connection

48 construction machine energy regeneration apparatus

49 assisting hydraulic cylinder

49 a cylinder portion

49 b piston portion

50, 51 connection

52 engine-assisting hydraulic motor

53, 53 a, 53 b boom communication passage

54, 54 a, 54 b arm communication passage

55, 55 a, 55 b movable weight communication passage

56 arm control valve

57 boom control valve

58 bucket control valve

59 turning unit control valve

60, 62 tank communication passage

61, 63 pump communication passage

64 arm remote control valve

64 a, 64 b, 65 a, 65 b, 66 a, 66 b, 67 a, 67 b communication passage

65 boom remote control valve

66 bucket remote control valve

67 turning unit remote control valve

68 a, 68 b bucket communication passage

69 a, 69 b turning unit communication passage

70 control circuit

71 first solenoid pilot valve

71 a first signal line

72 second solenoid pilot valve

72 a second signal line

73 controller

74 control hydraulic pump

75, 76 hydraulic circuit

77 relief valve

78 a, 78 b check valve 

1. A construction machine energy regeneration apparatus of a construction machine, the construction machine including a first operating part and a second operating part, which are driven by a hydraulic fluid, the first operating part including a boom, a turning unit, or a running unit, the second operating part including an arm, a bucket, or an engine-assisting hydraulic motor, the construction machine energy regeneration apparatus comprising: a movable weight provided in the construction machine and movable vertically; and a power-transmitting hydraulic circuit, which moves the movable weight upward by utilizing energy that is generated when the boom, the arm, or the bucket moves in a gravitational direction or energy that is generated when a brake is applied to bring the turning unit or the running unit to a stop, and utilizes potential energy of the movable weight as energy for driving the first operating part or the second operating part.
 2. The construction machine energy regeneration apparatus according to claim 1, comprising: a communication passage, through which a circuit of the first operating part or a circuit of the second operating part communicates with a circuit of the movable weight; and a switching valve, which is provided on the communication passage and which switches a flow direction of the hydraulic fluid in the communication passage, wherein the switching valve shifts to a first position when the boom, the arm, or the bucket moves in the gravitational direction or when a brake is applied to bring the turning unit or the running unit to a stop, such that the hydraulic fluid flows through the communication passage and the switching valve to move the movable weight upward, and the switching valve shifts to a second position when the movable weight moves in the gravitational direction, such that the hydraulic fluid flows through the communication passage and the switching valve to drive the first operating part or the second operating part.
 3. The construction machine energy regeneration apparatus according to claim 1, wherein the movable weight and a part of the power-transmitting hydraulic circuit have a function as a counter weight of the construction machine, and a total mass of the movable weight and the part of the power-transmitting hydraulic circuit is substantially equal to a mass of a counter weight required by the construction machine.
 4. The construction machine energy regeneration apparatus according to claim 1, wherein the movable weight is supported on a predetermined fulcrum and vertically swingable about the fulcrum by operation of a hydraulic cylinder.
 5. The construction machine energy regeneration apparatus according to claim 1, wherein the movable weight is configured to be movable in a linear direction.
 6. The construction machine energy regeneration apparatus according to claim 1, wherein the movable weight is supported on a predetermined fulcrum and vertically swingable about the fulcrum by operation of a hydraulic cylinder, the hydraulic cylinder includes a lifting cylinder and an assisting cylinder, a distance between the fulcrum and a connection where the lifting cylinder is connected to the movable weight is set to be greater than a distance between the fulcrum and a connection where the assisting cylinder is connected to the movable weight, the power-transmitting hydraulic circuit operates the lifting cylinder when the boom moves in the gravitational direction or when a brake is applied to bring the turning unit or the running unit to a stop, such that the movable weight swings upward, and the power-transmitting hydraulic circuit operates the assisting cylinder when the movable weight swings downward to drive the first operating part or the second operating part.
 7. The construction machine energy regeneration apparatus according to claim 1, comprising: a solenoid pilot valve, which supplies a pilot pressure liquid to a pilot port of the switching valve; a control valve, which controls a pressure and a flow rate of the hydraulic fluid supplied to the first operating part or the second operating part; a remote control valve, which supplies a pilot pressure liquid to a pilot port of the control valve; pressure sensors, which measure a supply pressure and a discharge pressure of the hydraulic fluid of the first operating part or the second operating part, or measure output pressures of the remote control valve, and generate pressure signals; and a controller, which receives the pressure signals and transmits a command signal to the solenoid pilot valve based on the pressure signals. 